Processes for preparing ring alkylated aromatic amines by contacting an aromatic amine and a hydrocarbon radical-providing source such as an olefin are widely known. Typical aromatic compounds which undergo such reactions include mononuclear aromatic compounds having one or more hydroxyl, amine or ester substituents. The alkylation of aromatic amines has been carried out in the presence of both homogeneous and heterogeneous catalyst systems.
Ring alkylated aromatic amines, which are readily prepared by the alkylation of aromatic amines, exhibit a variety of uses in commercial applications and are utilized as intermediates in the preparation of substituted isocyanates, herbicidal compositions, dyestuffs and textile auxiliary agents. Recently, aromatic amines have been utilized as chain extenders in the preparation of polyurethane systems.
Representative references which illustrate processes for alkylating aromatic amines include U.S. Pat. No. 4,760,184, assigned to Air Products and Chemicals, Inc., Trexlertown, Pa., which discloses a process for producing ring alkylated aromatic amines wherein an aromatic amine is reacted with an olefin, diolefin or an alcohol in the presence of non-zeolitic molecular sieve catalysts such as crystalline aluminophosphate and crystalline silicoaluminophosphate catalysts. Comparative example 1 discloses the alkylation of aniline with propylene over LZ-Y82, a steam stabilized HY zeolite, which was activated by heating at 95.degree. C. for 4 hours, followed by warming at a rate of 2.degree. C./min. to 400.degree. C. wherein the temperature was held for 4 hours.
U.S. Pat. No. 4,851,579, also assigned to Air Products and Chemicals, Inc., Trexlertown, Pa., discloses a process for alkylating aromatic amines to form ortho-alkylated products wherein an aromatic amine is contacted with an olefin or an alcohol in the presence of an ion-exchanged zeolite in which at least a portion of the exchangeable ion sites has been exchanged with aluminum cations. In a preferred embodiment, the catalyst is heated to about 400.degree. C. prior to the aluminum exchange step to remove residual sodium ions remaining in catalyst exchange sites.
U.S. patent application Ser. No. 370,486, assigned to Air Products and Chemicals, Inc., Trexlertown, Pa., discloses a process for selectively preparing N-alkylated aliphatic amines wherein cyclohexylamine is reacted with an alcohol or diol in the presence of a Y zeolite catalyst which has been impregnated with from 0.01 to about 15 wt % elemental phosphorus based upon the total weight of the impregnated catalyst. In a preferred embodiment, the impregnated Y zeolites are subjected to a thermal treatment wherein the catalyst is heated to temperatures ranging from about ambient to 800.degree. C., in an inert atmosphere for a period of 0.5 to 48 hours. This Application is not prior art assertable against the present invention.
U.S. patent application Ser. No. 370,440, also assigned to Air Products and Chemicals. Inc., Trexlertown, Pa., discloses a process for producing alkylene polyamines wherein an alkanolamine or diol is reacted with ammonia in the presence of a mordenite catalyst which has been impregnated with a phosphorus-containing moiety, under conditions sufficient to effect a condensation reaction. The catalyst may optionally be subjected to a thermal treatment wherein the catalyst is heated to temperatures ranging from 100.degree. to about 800.degree. C., in an inert atmosphere for a period ranging from 0.5 to about 48 hours. This Application is not prior art assertable against the present invention.
Although the prior art discloses a variety of catalytic processes for alkylating aromatic hydrocarbons and aromatic amines, these processes sometimes provide low conversion, poor reaction rate and are incapable of yielding a high ortho to para isomer ratio. A need in the art exists for a process which demonstrates high selectivity and conversion toward formation of ortho-alkylated aromatic amine products while also providing a higher rate of reaction than prior art processes.